Conventionally, in substitution for the high-frequency heating apparatus of this kind represented by electronic ranges, a so-called electronic range for general home use adapted to employ a commercial power source has been used in combination with an AC dynamo for exclusive use having a predetermined frequency and a predetermined AC voltage.
FIG. 22 is a view showing an arrangement of a prior art high-frequency heating apparatus. This is a drawing in which the high-heating apparatus is used in a sightseeing bus or the like. In FIG. 22, an engine 2 for generating transport power is provided in a car body 1 and the transport power is transmitted to tires 3 so as to transport passengers.
A so-called electronic range 5 is mounted in such a car body so as to perform microwave heating of a food 4. This electronic range 5 is constituted by a power source device 9 including a ferro-resonance type boosting transformer 6, a resonance capacitor 7 and a high-voltage diode 8, a magnetron 10 and an oven 11 and can be used by connecting a commercial power source for home use to terminals 12 and 13. Thus, in order to cause the electronic range 5 to exhibit normal functioning, it is essential to supply a predetermined voltage of, for example, 100 V to the terminals 12 and 13 at a predetermined frequency of, for example, 60 Hz.
Therefore, conventionally, by using an AC voltage generator 16 provided with a power generator 14 for exclusive use and a dynamo 15 actuated by the power generator 14, a microwave heating apparatus having an arrangement as shown is achieved by this AC voltage generator 16 and the electronic range 5 for home use and has been used in the motor vehicle.
On the other hand, due to the widespread of motor available, vehicles in recent years, long-distance transport, long-distance drive or outdoor leisures such as yachting, camping, etc. have become popular and thus, a demand has increased for drinking and eating at locations having no commercial power source, for example, in a motor vehicle.
Meanwhile, especially, in order to improve performance of catalysts for purifying exhaust gas of engines such as a diesel engine, a need for use of microwave heating has arisen.
Thus, the need for a high-frequency heating apparatus usable easily especially at locations having no commercial power source has increased.
However, based on the prior art described above, it was difficult to sufficiently meet increasing demand for use of high-frequency heating apparatuses at locations having no commercial power source. Namely, in the prior art, a special AC stabilizing power source capable of ensuring stability of frequency and voltage equivalent to those of the commercial power source is necessary and thus, a high precision AC stabilizing power source for exclusive use was absolutely necessary. This is because the ferro-resonance type transformer is employed in the power source device for driving the magnetron so as to stabilize the operation and output of the magnetron through its resonance with the resonance capacitor.
Therefore, the prior art high-frequency heating apparatus is very large, heavy and expensive due to the necessity of the AC stabilizing power source, ferro-resonance transformer, etc. and is difficult to handle due to its poor controllability. Especially, employment of the ferro-resonance type transformer means necessity of the AC stabilizing power source for exclusive use and thus, it was impossible to avoid the above mentioned inconveniences.
Therefore, it was difficult to manufacture at low cost, a high-frequency heating apparatus which is easily usable at locations where it is difficult to obtain a commercial power source, such as in a mobile space of a motor vehicle, a yacht, etc.